Three-dimensional (3D) viewing device and system thereof

Provided is a three-dimensional (3D) viewing device, comprising a body adapted to connect to a head-worn device, having a space therein, and a base side and opposite lateral sides neighboring thereto, the body comprising two openings symmetrically formed on the opposite lateral sides respectively; two displays disposed in the space; two light sources disposed in the space at the base side, and oriented toward the two displays respectively; and two sets of projection lenses disposed in the space at the two openings respectively, adapted to project the images of the two displays out of the two openings toward the two eyes of the head-worn device user, respectively. A 3D viewing and interacting system thereof is also provided.